Without a Thai bank account its impossible, that's why you need to get a non 0 90 day visa before you arrive that will allow you to open a bank account so you can get the retirement visa, no 90 day non O ,no bank account, no retirement visa,its that simple
Done mine this year get a certificate of residence from local immigration office get a medical from local clinic then do the online test once you pass the on line test go to a local driving license office and do the test foe depth of vision and traffic light test and pay for both licenses they will issues them same day took about 3 hours to do the simple tests and sort the licenses cot about 1500bht for both
The easiest way so you not need all the checks and medical insurance is to get a non o 90 day visa come to Thailand the open a bank account using the Non O visa then extend it to 12 months
Apply for a Non O 90 day visa ,no police checks ,no health insurance, get a bank account when you arrive then extend the visa to 12 month when in Thailand ,simple renew every year,you can pay the 800,000bht into your Thai account or pay an agent to do this for you and leave the money in your home country getting more interest that the agent costs,this visa can be renewed every year